The island is a heavily eroded volcano speculated to be over three million years old, surrounded by smaller islands including Ilheu Bom Bom, Ilh�u Caro�o, Tinhosa Grande and Tinhosa Pequena.
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The Black Tusk, a pinnacle of dark volcanic rock to the southeast, is also interpreted to be the remains of a deeply eroded volcano that was once covered with pyroclastic material.
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It is the most active volcano in Peru and is part of a north-south chain of three major stratovolcanoes, including the extinct and eroded volcano Hualca Hualca at the northern end, the dormant volcano Ampato to the south, and Sabancaya in the middle.
